Fire 2 Essay Example For Students

Fire 2 Essay IntroductionFire is a topic on which most people can comment. Fire is a widespread phenomenon. Most of us have seen fires in natural vegetation, or their effects; stark, blackened vegetation or a smoke pall. Because fires such as these can have damaging economic and social effects, can spoil forestry timber, can burn down houses and farms, and can kill people and animals, there has been a lot written about wildfires. Added to this wide perception of the damage that can be caused by wildfires, there has been increasing publicity given, since the 1950s, to the active use of fire as a management tool, particularly in protecting against severe wildfires. The introduction of a policy of deliberate burning as a management tool has a fascinating history, especially in the United States Forest Service, but the ecological effects of prescribing a fixed burning regime on large tracts of land are increasingly being questioned (Lyons, 1985, 3). To an ecologist, fire can be treated as just one of the many factors in an environment. It compares with droughts, floods, hurricanes and other physical disturbances because of the direct impact it makes on organisms. Unlike these physical factors, however, fire as a disturbing force is itself influenced by the biota, particularly the plant community. Alteration of the vegetation by any number of factors can influence the nature of a subsequent fire. Fire has similarities to grazing as a force on vegetation because of such feedback effects (Whelan, 1995, 20). Fire HistoryWhen cavemen learned to make and use fire, they could start to live in civilized ways. With fire, they were able to cook their food so that it was easier to eat and tasted better. By the light of torches, men could more easily find their way at night. They could also improve their wooden tools by hardening the points in fire. With fire to keep them warm, they could live in the colder regions and spread out over the Earth (CD-ROM, 1996). It is supposed that early people got fire accidentally from trees set ablaze by lightning or from spouting volcanoes. Then they carefully kept it burning in huts or caves. As far back as the study has gone, primitive peoples have never been found without fire for warmth and cooking. Fire also protected them from wild beasts (CD-ROM, 1996). In time people discovered how to create fire by rubbing dry sticks together. Then they invented bow drills to aid the process. When they began to chip flint to make axes, they found that hot sparks came from the stone. From this they later developed the flint-and-steel method of fire making. Later it was found that fire could be made by focusing the suns rays with a lens or curved mirror (CD-ROM, 1996). People remained ignorant of the true character of fire until 1783. In that year the great French chemist Antoine Lavoisier investigated the properties of oxygen and laid the foundation for modern chemistry (CD-ROM, 1996). Lavoisier showed that ordinary fire is due to the chemical process called oxidation, which is the combination of a substance with oxygen. He disproved the earlier phlogiston theory. The phlogiston theory held that when an object was heated or cooled it was due to a mysterious substance (phlogiston) that flowed into or out of the object in question (CD-ROM, 1996). Since fires are due to oxidation, they need air to burn properly, and a flame will go out after it has used up the oxygen in a closed vessel. Almost anything will combine with oxygen if enough time is allowed. Iron will rust if exposed long to damp air, and the rust is simply oxidized iron. When the chemical combination is so rapid that it is accompanied by a flame, it is called combustion (CD-ROM, 1996). Ignition Point or Kindling TemperatureHeat is required to start combustion. The degree of temperature at which a substance will catch fire and continue to burn is called its ignition point or its kindling point. A substance that can be ignited in the air is said to be flammable (or inflammable). The flash point of a flammable liquid is lower than its ignition point. The flash point is the temperature at which it gives off sufficient vapor to flash, or flame suddenly, in the air. It is not the temperature at which the substance will continue to burn (CD-ROM, 1996). When primitive peoples rubbed two sticks together to kindle a fire, they discovered without knowing it that the ignition point of wood is usually quite high. They had to use enough energy to create a good deal of heat before flames appeared. The tip of a match is composed of chemicals that, under ordinary circumstances, have a low ignition point. The heat created by scratching it once on a rough surface is enough to start combustion. It must be remembered, however, that the temperature needed to sustain combustion can vary with the condition of the substance and the pressure of the air or other gases involved, as well as with laboratory test methods (CD-ROM, 1996). Lowering the Temperature Puts Out FireAfter a fire has started, it will be self-supporting only when the temperature created by the combustion of the burning substance is as high or higher than its ignition point. This is one of the most important laws of fire. Some very hard woods, such as ebony, require a great deal of heat to burn. If the end of a stick of ebony is placed in a coal fire, it will burn. When it is drawn out, the fire of the smoldering ebony itself is lower in temperature than the ignition point of the wood. The flames thus will die (Lyons, 1985, 5). This principle explains why a match can be blown out. Ones breath carries away the heat, and the temperature falls below the ignition point of the matchstick. The stream of water from a firefighters hose cools the burning walls of a building with a similar result (Lyons, 1985, 5). The heat of a fire depends on the speed with which chemicals combine with oxygen. This speed depends generally on the quantity of oxygen present. If a lit match is touched to a small piece of iron wire, it will not burn. If a tip of a match is fastened to the end of the wire, struck, and plunged quickly into a jar of pure oxygen, the wire will catch fire and burn, with bright sparks shooting off briskly (Lyons, 1985, 6). Fire Without FlameFire may burn either with or without flames. A flame always indicates that heat has forced gas from a burning substance. The flames come from the combination of this gas with oxygen in the air. When a coal fire flames, it does so because gas is being forced from the coal, and the carbon and hydrogen in the gas combine with oxygen. If kept from burning, such gas can be stored. Manufactured gas is forced from coal in airtight kilns, or retorts. The product left after the gas is extracted from coal is called coke. Coke will burn without flame because no gas is driven off. In order to burn, the carbon in the coke combines directly with oxygen (Lyons, 1985, 8). It is the gas given off by the heated wax in a candle that produces the bright flame. When a burning candle is blown out, for example, a thin ribbon of smoke will arise. If a lighted match is passed through this smoke an inch (2.5 centimeters) above the wick, a tiny flame will run down and relight the candle (Lyon s, 1985, 8). Pearl Harbor EssayThe Natural Greenhouse EffectOn a planet with no atmosphere, the infrared radiation emitted by its surface would go straight out to space. But on Earth, things are very different. The Earths atmosphere has several gases that have the ability to absorb infrared radiation. This means that much of the infrared radiation emitted by the surface is captured before it gets out to space. As they absorb long-wave energy from the surface, these gases heat up, making the air warmer. This is roughly the same thing that happens inside a greenhouse on a sunny day, and why it is called the greenhouse effect. As you might expect, the gases that do this are called greenhouse gases (On-line, 1998). The atmospheres main greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and water vapor (H2O). Together they make up less than one-tenth of one percent of the atmospheres total volume. The rest of the atmosphere contains mostly nitrogen (78%) and oxygen (21%), neither of which trap much heat. The greenhouse gases are present in the atmosphere in just trace amounts. Even so, they have an extremely important role in determining climate. By trapping heat, they keep Earths thermostat set at an average temperature of +15 C. Without greenhouse gases, the average temperature would be 33C colder than it is now, and Earth would be a lot more like Mars-a frozen, dusty, lifeless planet (On-line, 1998). The natural greenhouse effect gives Earth an average temperature of +15C. Obviously, it isnt a steady +15 C everywhere on the planet. Some places are perpetually frozen, such as the polar ice caps. Others are constantly hot and humid, as in the tropical rai n forests. Other regions, like here in Canada, have highly variable seasonal climates-warm, wetsummers; long, cold winters. What is clear is that climate varies widely from place to place on the planet (On-line, 1998). Why do climates vary so much from place to place? The differences arise because the suns heat is not distributed evenly over the entire planet. Complicated interactions between the greenhouse effect, wind and ocean currents, land masses, elevation, and the many other factors distribute this heat around the planet in a way that creates the wide diversity of climates we can see. The interactions are so complex that they are nearly impossible to describe accurately, even with the help of the most powerful supercomputers (On-line, 1998). Natural Climate ChangeWe are surrounded by clues that climates have been different in the past. Many landscapes in Canada show traces of the last Ice Age, a time when climates were much colder than now. At the same time, fossils of tropical plants and animals have been found all over Canada, even in the high arctic. Clearly, the climates we now experience are different than those in the past. When did climate change in the past, and by how much (On-line, 1998)?The following graph shows the variations in global temperatures, going back one-million years. It shows that warm periods occurred roughly every 100,000 years, with colder periods in between. It was during those cold periods that the great continental ice sheets advanced, spreading over much of the North American continent each time (On-line, 1998). Figure 1 Variations in Global Temperatures Over the Last Million Years (On-line, 1998). The next graph shows how climates have changed in the past 1000 years. It shows that around 800 years ago, there was a 300-year warm spell. This was a time when Greenland was actually green (Europeans were farming there), and grapes and other warm-climate fruits could be grown on the British Isles (On-line, 1998). Figure 2Global Temperatures Over the Last 1000 Years (On-line, 1998)The graph above also shows that around 400 years ago, the global climate was approximately 1-2 degrees colder than now. It was a time when winters were longer, and glaciers advanced dramatically. The Vikings had to abandon their farms on Greenland, and withdraw from Eastern Canada, where they had also settled. This period is known as the Little Ice Age. It is clear that climates change naturally on their own. What has caused these changes? Scientists all over the world are studying this problem, and are coming up with many theories. Many natural events appear to have altered global climates, including meteo rite impacts, volcanic eruptions, and changes in the compositions of the earths atmosphere (On-line, 1998). The most important factor seems to be composition of the atmosphere, which affects the intensity of the Earths greenhouse effect. Scientists now know that many changes in past climates seem to occur at the same time that changes in the concentration of CO2 also occurred. When the Earths average global temperature has risen or fallen, CO2 concentrations have moved in a similar pattern (On-line, 1998). The last graph shows changes in temperature have been mirrored by changes in the two important greenhouse gases, carbon dioxide and methane. It shows that for every peak in average global temperature, there was a corresponding peak in greenhouse gases (On-line, 1998). The relationship between global temperatures and composition of the atmosphere has scientists extremely concerned. Human activities are rapidly increasing the concentration of greenhouse gases in the atmosphere. In fact, scientists now believe that if anthropogenic (human-caused) emissions of greenhouse gases are not significantly reduced, the Earth will warm at a rate faster than at any time in the 10,000 years that represent human history (On-line, 1998). Climate is usually something humans take for granted. It changes far too slowly for us to notice on a day-to-day basis. But by looking at long-term climate records, and with new techniques for determining ancient climates from ice, sediments, and other natural deposits, we can see climates have changed dramatically in the past. We can also see that some of the changes humans are making to the atmosphere and to landscapes are beginning to have noticeable effects on global climates. We now have to think about protecting the Earths climate system the same way we do about protecting other important parts of the environment, like water, air and soil (On-line, 1998). Figure 3Location of t he Principle F ire Events in 1 998 (On- l ine, 1998)ConclusionsFire provides the material well-being of the people in the industrial countries of the world. Heat from the burning of fuel converted into electrical and mechanical energy does practically all the work of these economies. However, the worlds population has a fire problem. Americans and Canadians lose property and life to fire at twice the rate of people in comparable circumstances in other industrial nations. The table below illustrates the fatalities due to fire in various nations (Payne, 1989, 56). Table 1Fire Caused Fatalities in Various Nations (Deaths per 100,000 pop.) (Payne, 1989, 56)Nation19741976-78Latest ReportCanada3.63.22.9United States2.92.92.8Sweden 1.61.51.6Japan1.51.5United Kingdom1.51.51.5France 1.51.51.5Australia1.50.8Germany0.90.90.9Switzerland0.70.60.7ReferencesComptons Interactive Encyclopedia: On compact disc (1996) CD-ROM. Lyons, John W. (1985). Fire. New York: Scientific American Library. Payne, Charles A., Falls, William R., Whidden, Charles J. (1989). Physical Science (5thed.). Iowa: Wm. C. Brown Publishers. Whelan, Robert J. (1995). The Ecology of Fire. Great Britain: Cambridge UniversityPress. United Nations Environment Program. On-line. Available:http://www.grid.unep.ch/fires/On-line. Available:http://www.piad.ab.ca